High strength alloys of zirconium



United States Patent 3,005,706 HIGH STRENGTH ALLOYS OF ZIRCONIUM Donald E. Thomas and Stanley Kass, Pittsburgh, Pa., as-

signors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed May 27, 1958, Ser. No. 738,003 5 Claims. (Cl. 75-177) This invention relates to zirconium alloys having high strength in combination with a high resistance to cor rosion by water at elevated temperatures.

In US. Patent No. 2,772,964, assigned to the assignee of the present invention, wherein one of the inventors of the present invention was a co-inventor, there are disclosed alloys of zirconium that are characterized by highly desirable properties for many applications. While the alloys of this US. patent have good strength properties both at room temperature and at temperatures of up to 600 F. there are applications which would be benefited if alloys of zirconium having equally satisfactory corrosion resistance properties but with substantial improvement both in tensile strength and yield strength while maintaining good ductility were available.

The object of the present invention is to provide zirconium base alloys embodying predetermined pro-portions of beryllium which alloys have enhanced mechanical strength properties, good ductility and a high resistance to corrosion to high temperature water and steam.

Another object of the invention is to provide a zir-' conium base alloy consisting of from 0.1% to 2.5% by weight tin, a total of from 0.1% to 2% by weight of at least one metal from the group consisting of iron, nickel and chromium and from 0.03% to 1.0% by weight beryllium, the alloy exhibiting high strength, good ductility and good corrosion resistance to high temperature water and steam.

Other objects of the invention will, in part, be obvious I and will, in part, appear herein-after.

In accordance with the present invention, novel improved zirconium base alloys characterized by high mechanical strength, good ductility, a high corrosion resistance to high temperature water and steam and being capable of hot and cold working have been produced. The zirconium base alloys consisting essentially of from 0.1% to 2.5 by weight of tin, a total of from 0.1% to 2%, by weight of at least one metal from the group consisting of iron, nickel and chromium, from 0.03% to 1.0% by weight of beryllium, less than 0.5% by weight of incidental impurities such as oxygen, nitrogen and carbon, as well as small amounts :of other elements, and the balance being zirconium. These alloys exhibit ultimate tensile strength and 0.2% yield strength values, both at room temperature and at elevated temperatures, substantially greater than those exhibited by similar alloys without beryllium. For employment in atomic reactors, especially pressurized water reactors and boiling water reactors, the alloys of the present invention are highly satisfactory because in addition to exhibiting maximum corrosion resistance, they have an extremely low neutron absorption cross section. The alloys of the present invention may be employed as structural members in nuclear reactors, as cladding for fission-able material, as cladding for control rods, and other applications. These alloys may be employed in conventional boilers and other apparatus wherein its combination of properties renders it highly useful.

The alloys of the present invention will function satisfactorily in nuclear reactors and be capable of being hot worked" even with substantial amounts of nitrogen of the order of 0.01% being present. Oxygen contents of up to 0.2% may be present in the alloys with no significant deficiencies being sufiered. Carbon may be Patented Oct. 24, 1961 ice present in amounts of up to 0.05 The alloys .of the present invention maybe hot forged, hot rolled, hot extruded, or swaged from ingots thereof. The hotworked alloys may be readily cold worked to produce members of desired final size and shape. The alloys will not crack during hot working if handled in a reasonable metallurgical manner. A

The following examples are illustrative of the present invention. In these examples all parts and percentages given for the compostion are by weight.

EXAMPLE I Table 1 Testing Temperature 0.2% Yield Strength (p.s.i.) 40, 000 18', 000 Tensile Strength (p.s.i.). 64,000 30,000 Uniform Elongation (Percent)- 14 17 Total Elongation (Percent). 18 28 Reduction in Area (Percent) 39 54 The results indicated in Table Icorrespond to the better average results obtained in working with alloy and preparing many members therefrom.

EXAMPLE II An ingot was prepared by consumable arc melting the following composition: tin 0.25%, iron 0.26%, beryllium 0.05% and the balance zirconium, except for small amounts of oxygen, nitrogen and carbon, as in Example I. The resulting 3 inch diameter ingot was extrudedto a inch diameter bar and tensile specimens were machined in the longitudinal direction from these bars and tested.

EXAMPLE III A 3 inch diameter ingot was produced by consumable arc melting and adding the following composition: tin .25 iron 26%, beryllium 0.15% and the balance zirconium. Oxygen, nitrogen and other impurities were present in amounts similar to Example I. The ingot was extruded into inch diameter bars which were then machined along a longitudinal direction into tensile specimens and tested.

EXAMPLE IV An ingot of 3 inch diameter was prepared by consumable arc melting the following composition: tin 0.25%, iron 0.28%, beryllium 0.35% and the balance being zirconium. Impurities such as oxygen, nitrogen and other impurities were in amounts similar to those in Example I. The ingot was hot extruded to inch diameter bars which were then machined, in a longitudinal direction into test specimens and tested.

EXAMPLE V An ingot of 3 inch diameter was prepared by consumable arc melting an alloy having the following composition'r' tin 0.23%, iron 0.25 beryllium 0.70% and the balance'being zirconium except for carbon, oxygen and 3 7 other impurities which were present in amounts similar to Example I. The ingot was hot extruded into /1 inch diameter bars and tensile specimens were then machined in a longitudinal direction and'tested.

The test specimens of Examples 11, III, IV and V were subjected to tensile tests both at room temperature and at 250 C. The resulting tensileproperties are as follows:

Table n ROOM TEMPERATURE 'rns'rs 0.2% Ultimate more Total an, Nominal Percent Be Y.S. 7 TS. EL, percent (p.s.i (p.s.i.) percent percent Table III 250 C. TESTS 0.2% Ys. Tomi 11.x, Nominal Percent Be (p.s.i.) T.S. (p.s.1.) EL, percent 7 7 percent 1 Surfaces defects noted on specimen prior to testing.

In Tables II and III, the abbreviations used are as follows:

Y.S. for yield strength T5. for tensile strength for elongation R.A. for reduction in area It will he noted in Tables II and III that tensile specimens from both the top and middle portion of each of the ingots were tested in order to determine the properties thereof. v

Further, short lengths from each of the extruded bars of Examples II, III, IV and V were hot forged to inch thick flats from which tensile specimens were machined with the following room temperature test results:

Corrosion tests were conducted in 680 F. water on all of the specimens of Examples I to V. The corrosion resistance of the alloys containing 0.05%, 0.15% and 0.35% Be was equivalent to that exhibited by specimens of Example I. The corrosion resistance of the alloy containing 0.70% Be was somewhat inferior. Thus, the alloys of Examples I to IV could be substituted for one another without any significant rise in corrosion rate.

EXAMPLE VI A series of 3 inch diameter ingots were prepared by are melting under vacuum the following zirconium base alloy, with and without additions of beryllium: tin 1.5%, iron 0.12%, chromium 0.10%, nickel 0.5% and nitrogen 60 ppm. maximum, zirconium balance. Portions of this base alloy were combined with beryllium to produce alloys containing 0.03%, 0.13%, 0. 62%, 0.82% and 1.74% beryllium, respectively. The six difl'erent alloys were hot worked into the flat specimens and the flat specimens were then tested for their corrosion resistance both in water at 680 F., in steam at 750 F. The following data in Table V indicate the relative corrosion resistance in terms of weight gain for the indicated number of days in the respective corrosive hot steam and water atmospheres.

Table V Wt. gain, mgJdm.

Wt. Percent Beryllium 141 Days in 168 Days in Steam Water It will be noted that the weight gain for the alloys of this invention having up to 0.62% beryllium is substantially the same within the experimental limits of the tests; From other data it has been found that for the alloys having up'to approximately 0.7% beryllium, the alloys exhibit a high corrosion resistance characteristic of the same alloy without beryllium. There is a slight increase in corrosion resistance in hot water for alloys containing between 0.7% and 1% by weight of beryllium. Above 1% beryllium the corrosion rate increases rapidly and significantly in hot water for the alloys of the present invention. Consequently, the preferred composition of the alloys with respect to the lowest corrosion rate in hot water and in hot steam is in the range of 0.03% to 0.70% beryllium.

The alloys of this Example VI will exhibit good me chanical properties while retaining good ductility up to 0.82% beryllium alloy. The alloys containing high quantitles of beryllium of over 1% will be less ductilethus the alloy with 1.74% beryllium will exhibit lower ductility.

It will be understood that the above description is only exemplary and not in limitationof the invention.

Alloys of essentially pure zirconium and beryllium in amounts of up to 1% lack the necessary corrosion resistance to hot water and steam. The same alloys with added tin in amounts of from 0.1% to 2.5% and from 0.1% to 2% of iron, nickel or chromium or combinations of two or all three, do exhibit a high corrosion resistance to hot water and steam.

We claim as our invention:

1. An alloy consisting essentially of from 0.1% to 2.5% by weight of tin, a total of from 0.1% to 2%, by weight of at least one metal from the group consisting of iron, nickel and chromium, from 0.03% to 1.0% by weight of beryllium, less than 0.5 by weight of incidental impurities, and the balance being zirconium.

2. An alloy consisting'essentially, by weight of from 0.5% to 2.5% of tin, from 0.057% to 0.5% nickel, from 0.05% to 0.5% iron, from 0.05% to 0.5% chromium, from 0.03% to 0.7% beryllium, less than 0.05% carbon, and incidental impurities not exceeding 0.5% and the balance being Zirconium.

3. An alloy consisting essentially, by weight of from 0.1% to 2% of tin, and from 0.1% to 2% of iron, from 0.03% to 0.7% of beryllium, less than 0.5% by weight of incidental impurities, and the balance being zirconium.

4. A member comprising a wrought and shaped body of an alloy consisting essentially of from 0.1% to 2.5% by weight of tin, a total of from 0.1% to 2% by Weight of at least one metal from the group consisting of iron, nickel and chromium, from 0.03% to 1.0% by Weight of beryllium, less than 0.5% by weight of incidental impurities, and the balance being zirconium.

5. A member comprising a wrought and shaped body of an alloy consisting essentially, by weight, of from 0.5

to 2.5% tin, from 0.05% to 0.5% nickel, from 0.05% 10 6 to 0.5% iron, from 0.05% to 0.5% chromium, from 0.03% to 0.7% beryllium, less than 0.05% carbon, and incidental impurities not exceeding 0.5% and the balance being zirconium.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN ALLOY CONSISTING ESSENTIALLY OF FROM 0.1% TO 2.5% BY WEIGHT OF TIN, A TOTAL OF FROM 0.1% TO 2%, BY WEIGHT OF AT LEAST ONE METAL FROM THE GROUP CONSISTING OF IRON, NICKEL AND CHROMIUM, FROM 0.03% TO 1.0% BY WEIGHT OF BERYLLIUM, LESS THAN 0.5% BY WEIGHT OF INCIDENTAL IMPURITIES, AND THE BALANCE BEING ZIRCONIUM. 